Dissipative Diamagnetism—A Case Study for Equilibrium and Nonequilibrium Statistical Mechanics

Using the path integral approach to equilibrium statistical physics the effect of dissipation on Landau diamagnetism is calculated. The calculation clarifies the essential role of the boundary of the container in which the electrons move. Further, the derived result for diamagnetization also matches with the expression obtained from a time-dependent quantum Langevin equation in the asymptotic limit, provided a certain order is maintained in taking limits. This identification then unifies equilibrium and nonequilibrium statistical physics for a phenomenon like diamagnetism, which is inherently quantum and strongly dependent on boundary effects. In addition we have shown that our results are directly connected with fluctuation induced diamagnetic susceptibility of superconducting grains. PACS Number: 03.65.Yz, 05.20.-y, 05.20.Gg, 05.40.-a, 75.20.-g     

Pharmaceutical grade sodium [99mTc] pertechnetate from low specific activity 99Mo using an automated 99Mo/99mTc-TCM-autosolex generator

Performance study of a computer controlled automated closed cyclic module for the separation and recovery of ^99mTc from low specific activity (n, γ) ⁹⁹Mo using methyl ethyl ketone (MEK) solvent extraction technique named ⁹⁹Mo/^99mTc-TCM-AUTOSOLEX (Technetium automated solvent extraction) Generator is described. The entire system is automated and controlled by a user-friendly PC based graphical user interface that actually supervises process via an embedded system based electronic controller. The average yield of separation of ^99mTc was above 85 % and ⁹⁹Mo breakthrough in ^99mTc pertechnetate was <0.002 %. The sodium pertechnetate obtained was a clear solution having pH 6–7, Radiochemical (RC). Purity >99 %, MEK content <0.1 % (v/v), Al and Mo content <10 µg/ml. R. C. Purity of ^99mTc-radiopharmaceuticals studied was not less than 96 %. Bio-Quality control studies confirm that sodium pertechnetate obtained was sterile and pyrogen free. Imaging studies in animals and humans with limited radiopharmaceuticals show that the quality of ^99mTc-pertechenate obtained in the present module was good enough to do clinical study.     

DNA Intercalating RuII Polypyridyl Complexes as Effective Photosensitizers in Photodynamic Therapy

Six substitutionally inert [Ru^II(bipy)₂dppz]²⁺ derivatives (bipy=2,2′‐bipyridine, dppz=dipyrido[3,2‐a:2′,3′‐c]phenazine) bearing different functional groups on the dppz ligand [NH₂ ( 1 ), OMe ( 2 ), OAc ( 3 ), OH ( 4 ), CH₂OH ( 5 ), CH₂Cl ( 6 )] were synthesized and studied as potential photosensitizers (PSs) in photodynamic therapy (PDT). As also confirmed by DFT calculations, all complexes showed promising ¹O₂ production quantum yields, well comparable with PSs available on the market. They can also efficiently intercalate into the DNA double helix, which is of high interest in view of DNA targeting. The cellular localization and uptake quantification of 1 – 6 were assessed by confocal microscopy and high‐resolution continuum source atomic absorption spectrometry. Compound 1 , and especially 2 , showed very good uptake in cervical cancer cells (HeLa) with preferential nuclear accumulation. None of the compounds studied was found to be cytotoxic in the dark on both HeLa cells and, interestingly, on noncancerous MRC‐5 cells (IC₅₀>100 μM ). However, 1 and 2 showed very promising behavior with an increment of about 150 and 42 times, respectively, in their cytotoxicities upon light illumination at 420 nm in addition to a very good human plasma stability. As anticipated, the preferential nuclear accumulation of 1 and 2 and their very high DNA binding affinity resulted in very efficient DNA photocleavage, suggesting a DNA‐based mode of phototoxic action.     

Studies on Antimicrobial Evaluation of Some 1-((1-(1H-Benzo[d]imidazol-2-yl)ethylidene)amino)-6-((arylidene)amino)-2-oxo-4-phenyl-1, 2-dihydropyridine-3,5-dicarbonitriles

A new series of 1-((1-(1H-benzo[d]imidazol-2-yl)ethylidene)amino)-6-((arylidene)amino)-2-oxo-4-phenyl-1,2-dihydropyridine-3,5-dicarbonitriles (4a–o) have been synthesized for the development of antimicrobial agents. Newly synthesized compounds were evaluated for their in vitro antibacterial activity against Gram-positive bacteria (Pseudomonas aeruginosa, Streptococcus pyogenes), Gram-negative bacteria (Escherichia coli, Staphylococcus aureus), and antifungal activity (Candida albicans, Aspergillus niger, Aspergillus clavatus). These compounds were characterized by infrared, ¹H NMR, ¹³C NMR, and mass spectra. The synthesized compounds 4b, 4e, 4 h, and 4k showed potent antimicrobial activity against tested microorganisms.     

New Heat-Resistant Polymers. Synthesis and Characterization of Polyamideimides from N-(4-Carboxy Phenyl) Trimellitimide and Benzidine

A new heat-resistant polymer has been synthesized from N-(4-carboxy phenyl) trimellitimide and benzidine. The polymer was characterized by nitrogen analysis, IR spectroscopy, density, viscosity, and x-ray measurements. The polymer was found to be insoluble in all polar organic solvents and only soluble in formic acid and concentrated H₂SO₄. The solubility parameter value has been determined. Thermal studies show that the polymer is thermostable up to 300°C. The electrical properties have also been measured.     

Filled and empty states of carbon nanotubes in water: Dependence on nanotube diameter, wall thickness and dispersion interactions

We have carried out a series of molecular dynamics simulations of water containing a narrow carbon nanotube as a solute to investigate the filling and emptying of the nanotube and also the modifications of the density and hydrogen bond distributions of water inside and also in the vicinity of the outer surfaces of the nanotube. Our primary goal is to look at the effects of varying nanotube diameter, wall thickness and also solute-solvent interactions on the solvent structure in the confined region also near the outer surfaces of the solute. The thickness of the walls is varied by considering single and multi-walled nanotubes and the interaction potential is varied by tuning the attractive strength of the 12–6 pair interaction potential between a carbon atom of the nanotubes and a water molecule. The calculations are done for many different values of the tuning parameter ranging from fully Lennard-Jones to pure repulsive pair interactions. It is found that both the solvation characteristics and hydrogen bond distributions can depend rather strongly on the strength of the attractive part of the solute-water interaction potential. The thickness of the nanotube wall, however, is found to have only minor effects on the density profiles, hydrogen bond network and the wetting characteristics. This indicates that the long range electrostatic interactions between water molecules inside and on the outer side of the nanotube do not make any significant contribution to the overall solvation structure of these hydrophobic solutes. The solvation characteristics are primarily determined by the balance between the loss of energy due to hydrogen bond network disruption, cavity repulsion potential and offset of the same by attractive component of the solute-water interactions. Our studies with different system sizes show that the essential features of wetting and dewetting characteristics of narrow nanotubes for different diameter and interaction potentials are also present in relatively smaller systems consisting of about five hundred molecules. We dedicate this work to Professor Debashis Mukherjee on his 60th Birthday.     

Chronological orderings of interval digraphs

An interval digraph is the intersection digraph of a family of ordered pairs of intervals on the real line; the family is an interval representation of the digraph. It is well known that an interval digraph has many representations that differ in the order of the endpoints of the intervals on the line. This paper generalizes the corresponding results on interval graphs by Skrien [Chronological orderings of interval graphs, Discrete Appl. Math. 8 (1984) 69-83] and describes how, given an interval digraph, the order of intervals of one representation differs from another.     

Dynamical analysis of a plant-herbivore model bifurcation and global stability

The first part of the paper deals with a brief introduction of the plant-herbivore model system along with deterministic analysis of local stability and Hopf-bifurcations. The second part consists of stability analysis of the limit cycle arising from Hopf-bifurcation and uniqueness of limit cycle. The third part deals with the study of global stability of the model system under consideration.     

Role of Skin Layers on Mechanical Properties and Supercontraction of Spider Dragline Silk Fiber

Spider dragline silk is a composite biopolymer that harbors extraordinary mechanical characteristics, and consists of a hierarchically arranged protein core surrounded by outer “skin” layers. However, the contribution of the successive fiber layers on material properties has not been well defined. Here, the influence of the different components on the physicochemical and mechanical properties of dragline is investigated. The crystal structure and the mechanical properties are not changed significantly after the removal of skin constituents, indicating that the core region of dragline silk fibers determines the structural and mechanical properties. Furthermore, the outer layers have little influence on supercontraction, suggesting they do not function as protection against the penetration of water molecules. On the other hand, the outer layers offer some protection against protease digestion. The present study provides insight into how the function and structure of silk fibers are modulated and facilitates the design of silk‐inspired functional materials.